What does that mean?
Try explaining better what the problem is. You should also mention what you have installed in addition to what ISPConfig perfect server guide tells to install. Like that mod_pagespeed.

I second the opinion from @Taleman that these folders are intended to be there and not related to the spam issues, these are cache folders from mod_pagespeed.

Regarding your spam issue, when you have spam emails in the outgoing mail queue (check with "postqueue -p" command), then you can inspect their headers with the command 'postqueue -q QUEUEID' where QUEUEID has to be replaced with the queue ID that you see in postqueue -p list (the ID is the char/number string that identifies the email). There are different reasons for spam, the most common ones are that someone got the password of an existing email account or that a website was hacked. You might also want to scan your web server for malware, e.g. with the free trial scan from ISPProtect.